Methods For Patient-Specific Shoulder Arthroplasty

ABSTRACT

A method of determining an optimal position of a glenoid implant. The method includes identifying a center point of a patient&#39;s glenoid fossa based on an image of the patient&#39;s glenoid fossa; determining the optimal position of the glenoid implant based on the location of the center point relative to a medial point of the patient&#39;s scapula; and selecting orientation of an alignment pin based on the determined optimal glenoid implant position such that the glenoid fossa will be prepared to receive the glenoid implant at the optimal position when the glenoid fossa is prepared with a cutting device or guide coupled to the alignment pin.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/552,079, filed on Oct. 27, 2011, the entire disclosure of which isincorporated herein by reference.

This application is related to the following concurrently filed UnitedStates patent applications, each of which is incorporated herein byreference: “Patient-Specific Glenoid Guides” (Atty. Doc. No.5490-000950/US); “Patient-Specific Glenoid Guide” (Atty. Doc. No.5490-000950/US/01); and “Patient-Specific Glenoid Guide and Implants”(Atty. Doc. No. 5490-000950/US/02).

FIELD

The present disclosure relates to methods for patient-specific shoulderarthroplasty.

BACKGROUND

This section provides background information related to the presentdisclosure, which is not necessarily prior art.

The shoulder joint is the third most replaced joint in the body. Duringsurgery, a Steinman pin is often used as an instrument guide. TheSteinman pin is placed in the scapula, and is precisely positioned toguide the reamer to prepare the joint for an implant that will recreatenatural version/inclination in the joint, or any other desiredversion/inclination. The pin is typically positioned based on a visualassessment of the joint and the surgeon's experience. While orientingthe pin in this manner is sufficient, a method and apparatus tofacilitate placement of the pin and recreation of natural version andinclination, or any optimal version and inclination, would be desirable.

SUMMARY

This section provides a general summary of the disclosure, and is not acomprehensive disclosure of its full scope or all of its features.

The present teachings provide for a method of determining an optimalposition of a glenoid implant. The method includes identifying a centerpoint of a patient's glenoid fossa based on an image of the patient'sglenoid fossa; determining the optimal position of the glenoid implantbased on the location of the center point relative to a medial point ofthe patient's scapula; and selecting orientation of an alignment pinbased on the determined optimal glenoid implant position such that theglenoid fossa will be prepared to receive the glenoid implant at theoptimal position when the glenoid fossa is prepared with a cuttingdevice or guide coupled to the alignment pin.

The present teachings also provide for a method of determining anoptimal position of a glenoid implant. The method includes identifying acenter point of the patient's glenoid fossa based an image of thepatient's glenoid fossa; determining the optimal position of the glenoidimplant based on a linear line extending between the center point and anarea proximate to a most medial surface of the patient's scapula; andselecting orientation of an alignment pin based on the determinedoptimal glenoid implant position such that the glenoid fossa will beprepared to receive the glenoid implant at the optimal position when theglenoid fossa is prepared with a cutting device or guide coupled to thealignment pin.

The present teachings further provide for a device for optimallypositioning a glenoid implant during repair of a patient's shoulderjoint. The device includes a patient specific surface designed to bereceived within the patient's glenoid fossa. An alignment pin guideextends from a first opening defined by the patient specific surface.The alignment pin guide is positioned and angled to guide insertion ofthe alignment pin into the glenoid fossa such that the alignment pinpasses through a center of the glenoid fossa towards a medial point ofthe patient's scapula, thereby orientating the alignment pin such thatthe glenoid fossa will be prepared to receive the glenoid implant at anoptimal position when the glenoid fossa is prepared with a cuttingdevice or guide coupled to the alignment pin. The device can be removedfrom cooperation from the patient's glenoid fossa without removing thealignment pin.

Further areas of applicability will become apparent from the descriptionprovided herein. The description and specific examples in this summaryare intended for purposes of illustration only and are not intended tolimit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only ofselected embodiments and not all possible implementations, and are notintended to limit the scope of the present disclosure.

FIG. 1 is a lateral view of a scapula and a damaged glenoid fossa inneed of repair, a center of the glenoid fossa is identified and used toidentify optimal version and inclination in accordance with the presentteachings;

FIG. 2A illustrates methods for achieving optimal glenoid version andinclination according to the present teachings;

FIG. 2B illustrates a processor, display, and input device forperforming methods according to the present teachings;

FIG. 3 illustrates providing optimal glenoid version and inclinationbased on the location of the center of the glenoid fossa relative to amost medial surface of the patient's scapula;

FIG. 4 illustrates providing optimal glenoid version and inclinationbased on the location of the center of the glenoid fossa relative to amost medial portion of the patient's medial glenoid fossa;

FIG. 5 illustrates use of a native glenoid face to provide optimalglenoid version and inclination; and

FIG. 6 is a perspective view of a patient specific alignment guideaccording to the present teachings coupled with a glenoid fossa.

Corresponding reference numerals indicate corresponding parts throughoutthe several views of the drawings.

DETAILED DESCRIPTION

Example embodiments will now be described more fully with reference tothe accompanying drawings.

With initial reference to FIG. 1, a human scapula is illustrated atreference numeral 10. The scapula 10 includes a glenoid fossa 12. Asillustrated, the glenoid fossa 12 is damaged, such as due to wear, andis in need of repair. To prepare the glenoid fossa 12 to receive animplant at predetermined, optimum version and inclination, which mayinclude natural version and inclination, the present teachings identifyand use anatomic landmarks and algorithms to design a patient specificalignment pin positioning guide, which is illustrated at referencenumber 50 of FIG. 6 and will be described further herein.

With additional reference to FIG. 2A, methods for orienting an alignmentpin, such as a Steinman pin for aligning a reamer, in order to provideoptimal glenoid version and inclination, are illustrated at referencenumeral 110. With initial reference to block 112, the center of theglenoid fossa 12 is first identified. The center of the glenoid fossa 12can be identified in any suitable manner.

For example, a three-dimensional (3D) model of the patient's scapula 10can be created based on CT images of the patient. The CT images can beprovided in the form of DICOM images, which typically include about 200CT image “slices” of the patient's scapula 10. Any suitable software canbe used to process the DICOM images to isolate the scapula 10 fromsurrounding bone or non-bony regions, such as “ORS Visual” segmentationsoftware from Object Research Systems. The 3D model of the scapula 10 isthen made from the images using any suitable software that can create a3D model, such as “ORS Visual.” The 3D model is then imported into anysuitable CAD software, such as Siemens NX or Solidworks, for example. Toidentify the center C, any suitable software (such as Siemens NX orSolidworks) or manual measurements based on the 3D model can be used, aswell as a combination of both.

For example, using the CAD software the center C or an approximationthereof can be identified with a best fit circle referenced off threeequally spaced points at the rim of the glenoid fossa 12. The locationof the center C can then be refined based on the location of each of thefollowing parts of the glenoid fossa 12: the anterior rim 14, theposterior rim 16, the superior rim 18, and the inferior rim 20. Theseparts of the glenoid fossa 12 can be automatically identified usingsuitable software, or can be identified manually using the CAD softwareby selecting points on the glenoid fossa 12, such as with a mouse(reference no. 154 of FIG. 2B, which is further described herein). Oncethe center C of the glenoid fossa 12 is identified, the center C can beused to identify orientation of a Steinman pin that will facilitatepreparation of the glenoid fossa 12 to receive an implant at apredetermined, optimal version and inclination, as described herein.

With reference to blocks 114-120 of FIG. 2A, the center C can be used tovirtually orient the alignment pin using suitable software, such as theSiemens NX CAD software, in a variety of different ways. FIG. 2Billustrates a processor 150, which can run the CAD software and DICOMimage processing software. A user can interact with and operate thesoftware using display 152 and a suitable input device, such as mouse154. With initial reference to block 114, a transverse plane (or line)that passes through both the center C of the glenoid fossa 12 and themost medial surface (MS) of the scapula 10 can be identified torepresent the position of the alignment pin to provide version control,as illustrated in FIG. 3. The most medial surface (MS) can be identifiedusing suitable software, such as the CAD software, or manuallyidentified on the display 152 using the mouse 154. The plane can beidentified manually and drawn on the CAD model using the mouse 154, orcan be identified using suitable software.

Inclination control can be identified using the natural inclination ofthe glenoid, which can be defined by marking two points, either manuallyusing the mouse 154 or automatically using the software. The first pointcan be on the superior rim 18 of the glenoid fossa 12, and the secondpoint can be on the inferior rim 20 of the glenoid fossa 12. Thealignment pin can be arranged such that it is perpendicular to a lineconnecting the inferior and superior points of the glenoid fossa 12, andextends along the line of FIG. 3, which extends through both the centerC of the glenoid fossa 12 and the most medial surface (MS) of thescapula 10. The pin can also be oriented about 8° inferior to the C-MSline, which is based on an average position of the general population,or at any other suitable angle. Inclination can also be determined bymatching a best fit sphere to the glenoid surface and connecting thecenter of the best fit sphere to the center C of the glenoid fossa 12,which can be performed manually using the CAD software or automaticallywith the CAD software and the mouse 154 or other suitable software runby the processor 150.

With reference to block 116, version control can also be defined byconnecting the center C of the glenoid fossa 12 to the most medial pointof the glenoid fossa 22, which is identified in FIG. 4 at MGV, with aline representing the position of the alignment pin either automaticallyor manually using the CAD software and the mouse 154. Other thanreferencing the most medial point of the glenoid fossa, the alignmentpin is virtually aligned in the same manner described above in thediscussion of block 114.

With reference to block 118 and FIG. 5, the native, undamaged face ofthe glenoid fossa 12 (to the extent present) can be used to reconstructanatomic version. If enough of the natural glenoid surface 30 ispresent, the surface can be mapped using the CAD software or othersuitable software to create an axis normal to the surface that passesthrough the center point C of the glenoid fossa 12. A best fit spherecan be used to create the orientation of the native glenoid surface.This created plane axis can then be used as the pin axis to orient thealignment pins.

With further reference to block 120, the inner cortex of the scapula 10can be referenced to orient the alignment pin. After the center C of theglenoid fossa 12 is identified, a plane can be drawn using the CADsoftware and the mouse 154 from the center C to an area midway betweenanterior and posterior cortices of the scapula 10. This will ensure thatthe alignment pin is placed directly in the center of the inner scapulacortex.

Once the alignment pin is virtually positioned on the display 152 asdescribed at blocks 114-120, the surgeon or other suitably trainedperson can adjust the virtual position of the alignment pin on thedisplay 152 as necessary at block 122 to customize version andinclination. For example, the alignment pin may be adjusted such that itdoes not extend directly through the most medial surface (MS) of thescapula 10, but is rather angled to meet patient-specific needs.

Once the desired orientation of the alignment pin has been virtually seton the display 152 using suitable software, a patient specific alignmentguide (FIG. 6 at 50) is formed, and then seated within the patient'sglenoid fossa 12 at block 122 of FIG. 2A. The alignment guide 50includes a patient specific surface 52 that corresponds to, and is anegative of, the patient's glenoid fossa 12. Extending from the patientspecific surface 52 are one or more alignment pin guides 54, such as afirst alignment pin guide 54A and a second alignment pin guide 54B. Eachof the guides 54A and 54B are sized and shaped to receive a firstalignment pin 56A and a second alignment pin 56B respectively. At block124, the first alignment pin 56A is inserted through the first alignmentpin guide 54A to within the scapula 10 during a regular “non-reverse”procedure, and the second alignment pin 56B is inserted through thesecond alignment pin guide 54B to within the scapula 10 during a reverseprocedure. The alignment pins 56A and 56B will be positioned accordingto the orientation assigned virtually using the software in order toprovide natural version and inclination, or any other predeterminedoptimal version and inclination.

With additional reference to block 128, after the first alignment pin56A or the second alignment pin 56B is set in the scapula 10, thealignment guide 50 is removed from the glenoid fossa 12. A suitablereamer is then coupled to the set alignment pin 56A or 56B, which willproperly position the reamer to prepare the glenoid fossa 12 to receivean implant at block 130 positioned to provide the predetermined optimalversion and inclination. At block 132, the implant is attached to theglenoid fossa 12.

The present teachings can also be adapted to a reverse shoulderprocedure. With a reverse procedure, the alignment guide 50 may beprovided with additional apertures surrounding the alignment pin guides54A and 54B to receive fasteners for a reverse shoulder glenoid baseplate. The base plate can be oriented to provide optimal version andinclination determined as set forth above. The inclination can be at aninferior tilt of about 10° in addition to the 8° inferior tiltidentified above.

The foregoing description of the embodiments has been provided forpurposes of illustration and description. It is not intended to beexhaustive or to limit the disclosure. Individual elements or featuresof a particular embodiment are generally not limited to that particularembodiment, but, where applicable, are interchangeable and can be usedin a selected embodiment, even if not specifically shown or described.The same may also be varied in many ways. Such variations are not to beregarded as a departure from the disclosure, and all such modificationsare intended to be included within the scope of the disclosure.

What is claimed is:
 1. A method of determining an optimal position of aglenoid implant comprising: identifying a center point of a patient'sglenoid fossa based on an image of the patient's glenoid fossa;determining the optimal position of the glenoid implant based on thelocation of the center point relative to a medial point of the patient'sscapula; and selecting orientation of an alignment pin based on thedetermined optimal glenoid implant position such that the glenoid fossawill be prepared to receive the glenoid implant at the optimal positionwhen the glenoid fossa is prepared with a cutting device or guidecoupled to the alignment pin.
 2. The method of claim 1, furthercomprising determining optimal version of the glenoid implant based onthe location of the center point relative to a most medial point of thepatient's scapula, the center point is identified using software runwith a processor.
 3. The method of claim 2, wherein the optimal versionof the glenoid implant is determined based on a linear line extendingfrom the center point toward the most medial point of the patient'sscapula, the linear line displayed on a display coupled with theprocessor.
 4. The method of claim 3, wherein the linear line is orientedabout 8° inferior to the most medial point of the patient's scapula. 5.The method of claim 3, further comprising designing a guide customizedto the patient's glenoid fossa, the guide including a receptacle fororienting the alignment pin relative to the linear line.
 6. The methodof claim 5, further comprising connecting a reamer to the alignment pinand reaming the glenoid fossa, the alignment pin guides the reamer toprepare the glenoid to receive the implant at the optimal position,including optimal version and inclination.
 7. The method of claim 1,wherein the optimal position of the glenoid implant is determined basedon the location of the center point relative to a most medial portion ofthe patient's glenoid vault.
 8. The method of claim 1, wherein theoptimal position of the glenoid implant is determined based on thelocation of the center point relative to an axis normal to a surfacethat passes through the center point.
 9. The method of claim 1, whereinthe optimal position of the glenoid implant is determined based on thelocation of the center point relative to an inner cortex of the scapula.10. The method of claim 1, further comprising determining the optimalposition of a reverse glenoid implant relative to a medial point of thepatient's scapula, and orienting the alignment pin at an inferior tiltabout 18° inferior to the most medial point of the patient's scapula.11. A method of determining an optimal position of a glenoid implantcomprising: identifying a center point of the patient's glenoid fossabased on an image of the patient's glenoid fossa; determining theoptimal position of the glenoid implant based on a linear line extendingbetween the center point and an area proximate to a most medial surfaceof the patient's scapula; and selecting orientation of an alignment pinbased on the determined optimal glenoid implant position such that theglenoid fossa will be prepared to receive the glenoid implant at theoptimal position when the glenoid fossa is prepared with a cuttingdevice or guide coupled to the alignment pin.
 12. The method of claim10, wherein the linear line is oriented about 8° inferior to the mostmedial point of the patient's scapula.
 13. The method of claim 11,further comprising preparing the glenoid fossa to receive the implant byconnecting a reamer to the alignment pin and reaming the glenoid fossa,the alignment pin guides the reamer such that the implant will providepredetermined glenoid version when connected to the glenoid fossa. 14.The method of claim 11, further comprising determining optimalinclination of the patient's glenoid by orienting the alignment pinperpendicular to a second line that extends between an inferior rim ofthe glenoid and a superior rim of the glenoid.
 15. The method of claim11, further comprising determining optimal inclination of the patient'sglenoid by matching a best fit sphere to the patient's glenoid fossa andconnecting a center of the best fit sphere to the center of the glenoidfossa.
 16. A device for optimally positioning a glenoid implant duringrepair of a patient's shoulder joint comprising: a patient specificsurface designed to be received within the patient's glenoid fossa; andan alignment pin guide extending from a first opening defined by thepatient specific surface, the alignment pin guide positioned and angledto guide insertion of the alignment pin into the glenoid fossa such thatthe alignment pin passes through a center of the glenoid fossa towards amedial point of the patient's scapula, thereby orientating the alignmentpin such that the glenoid fossa will be prepared to receive the glenoidimplant at an optimal position when the glenoid fossa is prepared with acutting device or guide coupled to the alignment pin; wherein the devicecan be removed from cooperation from the patient's glenoid fossa withoutremoving the alignment pin.
 17. The device of claim 16, wherein thepatient specific surface is formed based on images of the patient'sglenoid fossa and is a negative of the patient's glenoid fossa.
 18. Thedevice of claim 16, wherein the patient specific surface defines aplurality of second openings about the center opening configured toreceive mounts for a reverse shoulder implant.
 19. The device of claim16, wherein the alignment pin guide is angled to orient the alignmentpin about 8° inferior to a most medial point of the patient's scapula.20. The device of claim 16, wherein the alignment pin guide is alignedto orient the alignment pin about 18° inferior to a most medial point ofthe patient's scapula to position a reverse shoulder prosthetic glenoidat an inferior tilt.